Important Legal Question!

[Orophin]

If the Manderville goes viral on Youtube I know who to blame. :P

[UlricCraft]

SELL ME ONE.
It is the dance of my people.

[Remus]

You should be able to do it unless its only for yourself, but if you are selling it with that image on it then perhaps may need permission and stuff from SE.

[Welsper59]

I really wouldn't worry about it. You most likely won't get an official response neither, given the sort of abusive behavior your peers like to portray when given an inch. Creating something out of pure self-serving fandom is not much of a problem. It's when you distribute, and especially sell, the item in question that it becomes a legal issue. Even then though, small-time produced clothing is hardly a concern of theirs. If distribution is not your game, go for it. If they were that concerned about it, you'd never see anyone cosplay an FF character, bake cakes/cookies with FF symbolism, create fan sites, etc.

[Pandastirfry]

Actually I don't think they could copyright the steps of the "dance" itself, just the name, as far as I understand it. (I believe you can not copyright, movement and the human form in the US.)

Theoretically if you made the shirt, with a generic human form (think restroom signs, etc) and didn't specifically say it was the Manderville, or include their logos, you could actually sell it. However if you used the name and an image from the game/logos you'd run into trouble.